Cellulases are enzymes that hydrolyze the .beta.-D-glucosidic linkages in celluloses. Cellulolytic enzymes have been traditionally divided into three major classes: endoglucanases, exoglucanases or cellobiohydrolases and .beta.-glucosidases (Knowles, J. et al., TIBTECH 5:255-261 (1987)). Cellulases are known to be produced by a large number of bacteria, yeasts and fungi.
Primary among the applications that have been developed for the use of cellulolytic enzymes are those involving degrading (wood) cellulose pulp into sugars for (bio)ethanol production, textile treatments like "stone washing" and "biopolishing," and in detergent compositions. Cellulases are also known to be useful in detergent compositions for removing dirt, i.e., cleaning. For example, Great Britain Application Nos. 2,075,028, 2,095,275 and 2,094,826 illustrate improved cleaning performance with detergents that have incorporated cellulase. Additionally, Great Britain Application No. 1,358,599 illustrates the use of cellulase in detergents to reduce the harsh feel of cotton-containing fabrics.
Another useful feature of cellulases in the treatment of textiles is their ability to recondition used fabrics by making their colors more vibrant. For example, repeated washing of cotton containing fabrics results in a greyish cast to the fabric. This is believed to be due to disrupted and disordered fibrils, sometimes called "pills," caused by mechanical action. This greyish cast is particularly noticeable on colored fabrics. As a consequence, the ability of cellulase to remove the disordered top layer of the fiber and thus improve the overall appearance of the fabric has been found to be of value.
Because detergents, being a primary application of cellulase, operate generally under alkaline conditions there is a strong demand for cellulases that exhibit high activity at pH 7-10. Well characterized fungal cellulases, such as those from Humicola insolens and Trichoderma reesei, perform adequately at neutral to low alkaline pH. A number of enzymes demonstrating cellulase activity at high alkaline pH have been isolated from Bacillus and other prokaryotes, see e.g., PCT Publication Nos. WO 96/34092 and WO 96/34108. Thus, both fungal and bacterial cellulases have been investigated thoroughly. However, a third group of cellulases, those isolated from Actinomycetes, have attracted only meager attention. Wilson, et al., Critical Reviews in Biotechnology, 12:45-63 (1992), have studied cellulases produced by Thermomonospora fusca, Thermonomospora curvata and Microbispora bispora and have shown that many of these cellulases exhibit broad pH profiles and good temperature stability. Similarly, Nakai, et al., Agric. Biol. Chem., 51: 3061-3065 (1987) and Nakai, et al., Gene, 65:229-238 (1988) have demonstrated the alkalitolerant cellulase casA from Streptomyces strain KSM-9. This cellulase possesses an alkaline pH optimum and excellent temperature stability.
Despite knowledge in the art related to many cellulase compositions having desirable properties, including some examples from Actinomycetes, there is a continued need for new cellulases having a varying spectrum of characteristics useful as, for example, textile treatments, components of detergent compositions, pulp and paper treatments, animal feed supplements, processing aids for baking, and biomass converters. Applicants have discovered cellulases which possess such a complement of characteristics and which are useful in such known applications of cellulases.